Liquid crystal displays are widely used flat panel display devices. As is well known to those having skill in the art, a liquid crystal display includes a liquid crystal display panel that displays images using the variable transmissivity of liquid crystals in response to applied voltages. The liquid crystal display panel includes gate lines, data lines and an array of thin film transistors that are connected to the gate lines and the data lines. A data driver drives the data lines with a gray voltage, also referred to as a gray scale voltage, and is powered by a data driver supply voltage. A gate driver drives the gate lines with gate ON and OFF voltages, and is powered by a gate driver supply voltage. A timing converter is connected to the gate driver and the data driver to control timing of the gate driver and the data driver, and is powered by a timing converter supply voltage. The data driver, gate driver and timing converter may use different supply voltage levels. For example, the data driver supply voltage, gate driver supply voltage and timing converter supply voltage may be 3.3 volts or 5 volts. The gate ON voltage may be between 15 and 40 volts, and the gate OFF voltage may be between 0 and -15 volts. The gray voltage may be 5 volts or 10.5 volts.
The above-described voltages may be generated by a DC-to-DC converter that is part of the liquid crystal display. The DC-to-DC converter may receive supply voltages of 5 volts and 12 volts, and can convert these voltages to the various voltage levels described above.
In generating these voltages, it may be important that the various voltage levels are applied to the components of the liquid crystal display in a proper sequence, so that the liquid crystal display does not malfunction or become damaged. For example, if the gate ON or gate OFF voltage is generated before the timing converter supply voltage and the gate driver supply voltage, the gate ON and OFF voltage may be applied to the thin film transistors in the liquid crystal display panel before the timing converter and/or the gate drivers become operational. As a result, it is possible for the gate ON voltage or the gate OFF voltage to simultaneously turn on all of the thin film transistors. This may cause an excess amount of current to flow to the liquid crystal display panel and can result in a malfunction of the liquid crystal display panel and/or damage to the gate driver.
In order to reduce the likelihood that these problems may arise, the timing sequences in which the various voltages are applied to the various components of the LCD may be adjusted using an external device. The sequence of applying supply voltages to the various components may be set during manufacturing. Unfortunately, this may complicate the manufacturing process and may still result in improper operation of the liquid crystal display after manufacturing, which may damage the liquid crystal display.